years and through several notebooks--that his crucial analogy suffers
from a potentially fatal difference between the human body and the earth.
Both are built of the four elements of antiquity: earth, water, air, and
fire. But the human body sustains itself by circulating these elements,
particularly by maintaining some mechanism for permitting water (blood)
to rise from the legs to the head. The analogy of microcosm and macrocosm
can only work if the earth also possesses a comparable mechanism for sustenance
by cycling of elements.
But how can such a notion be defended for the planet, especially in
the light of the following problem: earth and water are heavy elements;
their natural motion can only be down (leading ideally to a planet of
four concentric layers with earth at the center, water above, air atop
water, and fire at the periphery). But if earth and water can only move
down, they must come to rest in two concentric spheres at the center of
the planet--and the macrocosm will therefore possess no device for
sustenance by circulation. Leonardo knows that he must therefore find
a mechanism that will make both earth and water move up, as well
as down, on our planet. This pressing need, so difficult to validate,
sets the central struggle that Leonardo exposes to our view throughout
the Codex Leicester.
Ironically, I wish to argue, he never did solve the problem for his
main subject of the codex--water. That is, he tried again and again,
but never found a satisfactory mechanism to guarantee the upward motion,
hence the cycling, of water. However--and this is the vital point
that has usually been missed--Leonardo did succeed (according to
his lights) in his quest to find a mechanism for upward movement of
the other heavy element: earth. Fossils on mountains provide the observational
proof that earth can rise, both generally and often. For marine shells
once inhabited the sea but now reside in the high mountains. The paleontological
observations received such prominence in the Codex Leicester
not, as has usually been argued, because fossils once lived in water
and the codex treats water in all major aspects (an awfully lame reason
for devoting so much space to paleontology) but rather because fossils
mark Leonardo's great success (in contrast to his failure for the central
subject of water) in illustrating a general mechanism for the upward
motion of earth, and therefore for a self-sustaining planet that may
legitimately be compared with the human body.
Leonardo knew only too well that he faced a serious problem
with the motion of water through the earth, and he virtually obsesses
over the issue in notebook after notebook, repeating the conundrum
in almost unchanging words and proposing various solutions, only to abandon them later as untenable. Water, by itself and following
its "natural course" (Leonardo's words) can only flow down. But
within the body of the earth, water also moves up to emerge as springs near
the tops of high mountains (and thence back on track, to flow as rivers
to the sea). An earthly force must therefore make water rise through the
land against its natural inclination to flow down. The combined action of
these two forces will cause water to circulate--and thereby act like
the blood in our bodies to sustain a living system:
So does the water which is moved from the deep sea up to the summits
of the mountains, and through the burst veins [Mountain springs] it
falls down again to the shallows of the sea, and so rises again to the
height where it burst through, and then returns in the same descent.
Thus proceeding alternately upwards and downwards at times it obeys
its own desire [to move down] at times that of the body in which it
is pent [to move up]. (From the Arundal Codex in the British
Museum).
Leonardo could not have been more explicit in admitting that water can
move up only by running against its natural course and that, if some mechanism
can |